Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754344Ab3F0WYP (ORCPT ); Thu, 27 Jun 2013 18:24:15 -0400 Received: from mail-pb0-f49.google.com ([209.85.160.49]:48104 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753900Ab3F0WYO (ORCPT ); Thu, 27 Jun 2013 18:24:14 -0400 MIME-Version: 1.0 Date: Thu, 27 Jun 2013 18:24:13 -0400 Message-ID: Subject: Re: [PATCH] nbd: correct disconnect behavior From: Paul Clements To: kernel list Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3104 Lines: 86 On Wed, Jun 26, 2013 at 7:21 PM, Andrew Morton wrote: > > On Wed, 19 Jun 2013 17:09:18 -0400 (EDT) Paul Clements wrote: > > This sounds like something which users of 3.10 and earlier kernels > might want, so I added the Cc:stable tag. Please let me know if > you disagree. That is a good idea. It would be useful in stable. > > --- a/drivers/block/nbd.c > > +++ b/drivers/block/nbd.c > > @@ -623,6 +623,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, > > if (!nbd->sock) > > return -EINVAL; > > > > + nbd->disconnect = 1; > > + > > nbd_send_req(nbd, &sreq); > > return 0; > > } > > @@ -654,6 +656,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, > > nbd->sock = SOCKET_I(inode); > > if (max_part > 0) > > bdev->bd_invalidated = 1; > > + nbd->disconnect = 0; /* we're connected now */ > > return 0; > > } else { > > fput(file); > > @@ -742,6 +745,8 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, > > set_capacity(nbd->disk, 0); > > if (max_part > 0) > > ioctl_by_bdev(bdev, BLKRRPART, 0); > > + if (nbd->disconnect) /* user requested, ignore socket errors */ > > + return 0; > > return nbd->harderror; > > } > > hm, how does nbd work... Hard to tell as nothing seems to be documented > anywhere :( I think most people look at the nbd-client to see. :) But I will work on some docs for the ioctls... Briefly, though, it goes something like this: nbd-client and nbd-server negotiate parameters, including the server telling the client how big the export is Then the nbd-client does a series of ioctls to set up the device: NBD_SET_SIZE - set the size of the device NBD_SET_SOCK - tell the kernel which socket to use NBD_DO_IT - this ioctl lasts for the life of the device and causes nbd-client to go into a receive loop, handling I/O replies from the nbd-server NBD_DISCONNECT, meanwhile, can be called from a separate thread (usually "nbd-client -d" calls it). This requests a disconnect of the device. > > > --- a/include/linux/nbd.h > > +++ b/include/linux/nbd.h > > @@ -41,6 +41,7 @@ struct nbd_device { > > u64 bytesize; > > pid_t pid; /* pid of nbd-client, if attached */ > > int xmit_timeout; > > + int disconnect; /* a disconnect has been requested by user */ > > }; > > The cool kids are using bool lately ;) Hey, maybe I want to be able to compile with gcc 2.7.2 ? :) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/